This is what I thought was Blade's main problem, when it's good, it's oh so very good, it just took it a long time to get there. Once Leangle shows up, things start moving a little faster, though not entirely because of Leangle, that's just the stage in the series I thought showed change a lot.The Undead just seem to me like they're trying to be the Grongi, the Unknown, and even the Orphnoch and Mirror Monsters in some instances, all at once - Both story/character-wise and design-wise. They just don't seem very original/interesting to me. The Worm were kinda like that themselves, perhaps to a lesser extent, I don't know.
I'm only up to episode 13 though, so maybe to Undead could grow on me. I'm just not interested at the moment.
Now, I see the Undead differently. True, they're somewhat of an amalgamation of previous villains, but a lot of them felt very human. It's not like the Orphnochs were they were humans at first and knew how to act as a human. The Undead learned, they began experiencing human emotions and learned how to convey them, even make sacrifices for them. I love seeing that sort of evolution in a series, especially from the enemies. Blade is one of those series that makes me think about what really makes a good protagonist and set of antagonist, what gives the riders the right to be the arbiters of whether or not the Undead should stick around. You have the riders fighting for humans and their right to live on earth, but on the flip side (sort of), you have the Undead doing the exact same thing.
Sort of reminds me of an old saying I used to hear "In war, you kill your enemies, but every time you do that, you've taken away someone's father, husband or son". It shows that the world can be a cruel place at times and be summed up as "survival of the fittest".
As you can see, I think of Blade as one of the more philosophical series in the franchise with what is easily the best set of villains in my opinion. It has just the right mix of ambiguousness and existentialist subject matter that so many other series try to shoot for but fail at. Though, being primarily targeted at children nowadays, it's sometimes hard to see this, but hey, it's fun to think about.